You do realize another reason why these big companies hold so much capital is due to the fact that many do not vote. Many are not politically active on any level. They buy their iPhones and cry foul when things don't​ go their way. Did they vote? Nope. You want your voice heard, keep speaking (voting). You also have to realize that donations come from people that work in various industries. You can't lump everyone that works in every industry together. There are people from both sides on Wall Street. To try to say otherwise would be foolish.
Politicians are people. Most want to just keep their jobs. If you made it important for them to reflect your values, believe me, they would. You can't get big money out of politics without putting people in power that advocate the removal of money from politics. Some on Wall Street want money out of politics. *Gasp* shocking I know